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hype7 writes "ThinkSecret is running a story which might explain exactly why the Dual 2GHz G5 machines have been delayed to the customers that ordered them minutes after the keynote was delivered. Apparently, Virginia Tech has plans to build a G5 cluster of 1100 units. If it manages to complete the cluster before the cut-off date, it will score a Top 5 rank in the Linpack Top 500 Supercomputer List. Both Apple and the University are playing mum on the issue, but there's talk of it all over the campus."

That's the one thing that favors huge amounts of processors in the same box. All this "the internet is one giant distributed computer" doesn't acknowledge this. A box designed to be separate just will not have the latency advantage of a supercomputer designed from the ground up.

Virginia Tech placed the dual-2GHz G5 order shortly after the G5 was announced. Multiple sources said Virginia Tech has ordered 1100 units

Wow, that'll make Apple's quarter for sure:-)

Seriously though, why PowerMacs ? I've always been under the impression that intelloid machines are the cheapest commodity hardware around for equivalent processing power, if not the most exciting. Would anybody know why Powermac G5s are a better choice here?

(Note to computer zealots: it's not a flamebait, it's a genuine question, from someone who is rigorously ignorant of the Mac world. And just in case, the first sentence is a joke, too...)

Of all the Macintosh rumor websites, Think Secret [thinksecret.com] is, by far, one of the most reliable sites I've seen. If it wasn't, I wouldn't be investing $1,200 a year in them for their message board [thinksecret.com]. Of course, if you think you can do better...;-)

Who builds 2-8K processors in a box? Have you thought for a second what it might take to power or cool this? Or if it could be wired? The actual engineering of actually doing this are much more challenging than talking crap on Slashdot.

A couple of things make them suitable for clustering:* There's heaps of processor-processor bandwidth and memory bandwidth.* On board gigabit ethernet.* Monster fast execution of properly written vector code.* Well designed cooling.

Of course, the bang/buck ratio could be an issue for some debate but there's little doubt that in comparison to other commercial unices it's an absolute bargain.

Right after the Sony Playstation 2 launch, there was a big shortage. Several media stories blamed it on some "unnamed" Middle East country buying them all up to power their missles and supercomputers (because, the rumor claimed, the PS2 was just so powerful).

Currently the top 5 consist of 4 machines that have a Therotical maximum speed (Rmax) the are larger then the 10TFLOPS this machine will have. Then you have to translate that into peak speed which is what matter and what this list uses to rank the machines. Peak will be a good deal less, but this mostly has to do with the way the systems are interconnected and not the machines themselves. Say what you may about the G5 but the interconnect is more important.

There is only one machine in the top 5 that this cluster could beat. The rest of the world has had 6 months to build machines too.

This should be a top 10 machine for sure. Good to see more fast machines being built every day.

Several years ago I did some work on some Virginia Tech "supercomputers" (actually, baby versions of ones on campus that were the same as huge ones they leased time on elsewhere), and I think the people talking about Altivec are on track. I never knew exactly what they did, but at that time the Math, CS, and Engineering groups were working together to simulate wing designs for the YF-22 jet figher prototype. Since I was more of a "sysadmin" (althoug h with a math and CS background) I ignored most of what was going on, but one thing I can tell you was vectors, vectors, and more vectors. The vector is king. It's an assumption, but I'll bet they are still working on similar type studies, and if built, this will be just the beast for it.

While the AltiVec unit is very impressive, The SSE2 unit on the P4 or the Opteron would have nearly the same performance and cost a whole heck of a lot less (I am betting if this rumor is true at all, then Apple has given the units to the school).

What I am wondering is, what OS is this cluster going to run? I mean, have the BSD folks figured out how to scale? No chance it will be OS X...maybe AIX?

The grant money that flows into a public research and occasionally teaching institution can be stagering, and absolutely dwarf the money students pay in tuition (sometimes by a factor of 10!). A better question might be, why don't the gradstudents donating their labor, possibly to patents that will be controlled by the university, recieve more consideration, and fair labor law protections.

But I would bet this will be not too dissimilar in use from the HP Itanium2 referenced earlier on slashdot. I would bet one of the paramount concerns this cluster would look at is the effect of farm runoff, and probably climatology too among other things.

1) As others have mentioned, AltiVec and the dual-FPU on the G5 probably were significant factors in this decision. The Earth Simulator is comprised of processors that are very slow at most tasks, but are designed to scream at vector-optimized code and, honestly, AltiVec makes SSE2 and 3Dnow! look like toys by comparison.

2) You would be hard pressed to configure a dual-opteron or dual-Xeon which could trounce the G5 in terms of speed and cost significantly less. MacOS X server also costs less than any version of windows (pure capital cost here for an 1100 seat license), which may also have factored in.

3) My guess is that they have struck a fairly significant deal with Apple (even so low as Apple provides them at cost, though I doubt its quite that low) in exchange for some degree of publicity when this thing is built.

With 1100 machines in the cluster, there must be _at least_ 2200 DIMMs. Since these must be 400MHz (PC3200) DDR, they can't be on a large 0.15 micron DRAM process, but most likely between 0.11 and 0.13u.

Who cares?

APPLE G5'S DO NOT SUPPORT ECC.

The random bit error rate for 2200 DIMMs with 0.13u cells is roughly one '1' bit dropped to '0' every 9 hours. In other words: good luck getting any reliable, large-scale computation done with this cluster. (And I do mean "good luck" - they might get a run of two or three days without any problems once in a while.)

Now if only Apple would support PC3200 ECC DIMMS, which certainly do exist:

I wonder if any universities have tried to write a distributed computing app along the lines of seti. Require it to connect to the university network, it grabs itself maybe 50 megs of hd space, and a fraction of all the new computers people bring to campus, in addition to all the computer lab gear belong to their massive number crunching problems. Make another version available to alumni, or even institutions as some form of corporate sponsorship.

Then if it got popular, and they were really clever, they could sell off a part of that computational power they amassed to solve other peoples problems providing for funding for new versions and new supercomputing clusters.

It's not just a campus rumor. I attended an informational meeting about it today (which was actually postponed when I got there, so there will be another one soon). Basically, they are recruiting a few computer geeks here at Tech to help set it up and all. Should be fun:P

Latency is paramount for some tasks, less important for those that *can* make a good distributed project over the Internet of today.

Now, since today's supercomputers are *all* massively parallel constructions, the difference between a commercial design and an off-the-shelf cluster is in the quality and speed of the interconnects. NEC's Earth Simulator, the prime example of 'custom' supercomputer architecture, puts many processor units on *ridiculously* fast 'local' buses, and its racks are all interconnected with still_pretty_insanely_fast (and rather expensive) custom links.

Meanwhile, more 'commercial' designs use various interconnects. IIRC, NEC's 'regular' supercomputers, which formed the design basis for the Earth Simulator architecture, use Fibre Channel 'mesh' networks between racks. The Opteron - sure to be an up-and-coming player in this market - offers HyperTransport, which it looks like Cray will be stretching to its limits on Red Storm; I'm not sure *how* long an HT bus can be, but one gets the impression they'll be stretching it as far as possible, and it's certainly high throughput/low-latency versus the technologies you'd usually find in use for 'networking.'

Anyhow, point is, those designs pack a lot of CPUs together with *very* fast interconnects (equivalent to 16, 32, 64+-way SMP), and have lots and lots of racks of those. (The Opteron/Red Storm approach sounds sexy to me, because I think Hypertransport should let them pack 'lots and lots' of CPUs together versus existing designs. I've yet to read anything about what they're actually doing with it, though.)

Now.. In contrast, an 'off the shelf' cluster is usually going to stick with Ethernet, and will only have 1 to perhaps 4 processors per [node-unit-where-the-CPUs-are-connected-on-a-fast- local-bus], depending how affordable 'cheap' multiprocessor systems are at the time. But *everyone* building supercomputers bumps up against the latency/routing problem; it's just a question of whether it's a problem for, say, 50 Earth Simulator racks (aren't there quite a few more?) vs. 1100 PowerMacs. Experimenting with 'lots of little nodes' has led us to better understand the problem, and learn how to produce tuned topologies that can compete favorably with 'purpose-built' hardware. See: http://aggregate.org/KASY0/ [aggregate.org]

Now, the question *is* one of cost-benefit. Large supercomputers tend to be built with maintenance features and power efficiency in mind. In turn, a totally 'off the shelf' cluster like KASY0 has some advantages because each machine is a cheap, practically disposable 'module' unto itself, and can doubtless be downed off the cluster, pulled out and replaced with another while being easily bench-repaired (since, after all, it's a self-contained PC, rather than a CPU blade or some other random card that would require an expensive test rack to troubleshoot). Meanwhile, if you absolutely demand low-latency, you want one sort of design (Red Storm seems to be acheiving it 'on the cheap,' by combining off-the-shelf - and thus cheap - chips and buses with smart 'custom-design' engineering) while if you can sacrifice some for throughput (jobs with few conditionals), you want another... (like 1100 G5 Macs on a shelf, wired with 'boring' gigabit ethernet, especially if Apple is giving you a bulk discount on the hardware).

So what I'm trying to say is... this is a *combination* of PR stunt and intelligent planning, and there's certainly a lot of 'good science' they could do with the beast - both in number-crunching and 'computer science' a-la cluster topologies. Whether they'll actually *use* it for such, or if it'll be solely a topology toy is anyone's guess.

I think there's some hope that it'll be the "Real Thing," though, since this would explain some of the weird rumors about FC-on-the-mainboard Macs. So they get a Real Monster, made of what will be revealed as "the new G5 Xserves" at the unveiling. The best of COTS *and* fresh d

i would take this story to imply that a G5 powered Xserve is not going to be shipping anytime soon..... the Xserve is made to cluster and run in situations like this. i guess the rumor sites can speculate if it's G5 parts available or some other holdup on a G5 Xserve.unless there is some reason the desktops are better for this project that i did not pick up on?

as for the above question about Macs.... depending on what they want to really do with this, Altivec is really efficient for some computations. all flame wars aside there have always been people clustering Macs for certain uses. i do not know how much of it was user preference or the software they wanted to run or the simplicity of getting the cluster running.it is supposedly VERY simple to cluster Macs. there was a story on/. a year or so ago about a group that went from building a rack and unboxing their G4s to a running cluster in part of a day. i really don't remember the specifics but i think it was something like 30 G4s? i would guess the G5 is not that much harder... and they seem to have Apple helping. maybe they hooked up the optical cards from the Xserve...... we'll see i guess.

Funny, I haven't heard anything about it prior to today. Guess I'm just out of the loop then...

As a University of Virginia staff person, I can tell you that VT's impending purchase of 1100 G5's was announced on our Mac user's group email list back on 28 July. By Apple's regional Higher Education user's group rep, who kiddingly asked when they could expect UVa's purchase order for 1200...

Have you seen the size of the heat sinks on the G5? I saw one in an Apple store today and was very impressed with the engineering of the whole machine.

The heatsink is a large oblong about 5"x4"x6" with a thin grille like construction. It's just too big to go in the 1U Xserve. Give them some time to work on designing it to fit though. The G5 is an ideal CPU for the Xserve as you say.

Or how about this: your bandwidth is dependent upon the amount you contribute to the distributed processing.

Hopefully there would be some sort of minimum service level, maybe 64kbps; presumably people dropping tens of thousands expect at least a modicum of return on their investment. People who didn't want to install the client could trudge along at those speeds.

Eventually there would be a market system, whereby people would trade their completed blocks for other commodities, like food vouchers, prints, copies, cash, and sexual favours.

According to Apple, there were "over 100,000" pre-orders for the G5. Now this includes single processor models, but the university's alleged order of 1100 machines is not going to make a big impact on everyone else.

Besides, the real reason that Apple's machines are late is case defects and AGP problems, amongst other issues that Apple has not been forthright about. At the keynote an honest Apple employee told me the machines wouldn't ship until October as there were many little problems and I should wait for the January refresh so I don't get a flaky machine.

And one has to wonder why anyone building a cluster would build it using desktop machines and not use the forthcoming G5 rackmount machines from Apple and IBM... which is supposed to include a quad-processor from IBM.

When calculating FP throughput for G4 or G5 machines, don't forget that both chips support 4-wide single precision SIMD FP including fused multiply-add operations. A 970 doing single precision FP vector work would potentially see a big improvement even over its dual scalar FPU's in throughput.

Yes and no. The degree to which a cluster suffers from node-to-node latency depends on the inter-node interconnect used. However, the choice of interconnect cannot remove inter-node latency. When Node X needs to work on data set Y, the cluster controller has to send data set Y to Node X over the interconnect. Data has to be copied into Node X's memory (or onto Node X's disk, if the data set is large). This is not true in a supercomputer. So while you can lower the node-to-node latency, you cannot eliminate it in a cluster.

Isn't it premature to draw conclusions until we better understand how Apple and Virginia Tech plan to architect this new super type computer cluster?

Depends on the conclusion.:) We can conclude, for example, that this cluster will not perform at the same level as a supercomputer with comparable FLOPS, unless the problem can be divided up into data sets that are small enough to fit into a single processor's cache. (Once the data is resident in each node's cache, the difference between cluster and supercomputer disappears, because there is no node-to-node communication at all until the given compute cycle is complete.)

If the data set can be parallelized that easily, then they probably wouldn't use G5's, because the problem wouldn't benefit from vectorization as much as we're all assuming theirs does.

That still doesn't change the fact that Apple apparently delayed tens of thousands of G5 shipments for a month, making other companies and individuals all wait just to please this one university. If I had lost my place in the queue, I wouldn't be happy having to wait longer for a machine I likely ordered three months ago.

Now what maybe true is that because these machines are going into a cluster, they don't care about cosmetic problems with a patched case door and they don't care if AGP 8X doesn't work right for high-performance 3D cards. So Apple could be dumping 1100 "good for clusters" machines on the university while waiting for an inline revision of the first batch of G5's. That makes more sense.

And you know... I'm quite glad I took an honest Apple employee's advice and don't have to worry about this stuff. Come January (Feburary is what I put on the calendar), I'll have a G5 with some of the bugs worked out and for less money.

So how does this anti-intellectual tripe qualify as insightful? Any yahoo can point at and complain about just about any non-trivial project at a research university whether it is public or private. If they were building it just to attain a certain ranking without any research proposals or plans it wouldn't be hard to find fault. Does anyone that could possibly be the case here? I think this sort of empty headed bushwhacking is a cheap shot and contemptible.

Is there something particularly about building any clusters today that is ill advised? Anything specifically about a cluster built with these parts? Why do any science that involves a large expense when the money could be applied to "lowering tuition"? Maybe because an important part of the mission of some universities is to advance the state of knowledge by performing research that would not be done by other segments of society.

Heat. CPUs create quite a lot, some more some less (like the G5). A few years ago a German university (Chemnitz IIRC) build a large Linux cluster. For cost and speed reasons they wanted to go with Athlons, but decided to use P3s instead, mostly because they created less heat. It is one thing to pack a couple of hundred computers into a building, it's an other to also buy a new air-conditioning for that building.

I am one of the designers of KLAT2 [aggregate.org] and KASY0 [aggregate.org], and the guy who ran the Linpack benchmarks on both. Over 3 years ago when we submitted our results for KLAT2 to the top500 list, there was no public indication that 64-bit floating point was required. It took them awhile, but the top500 website now has a FAQ that indicates "full precision" [netlib.org] is required, and they interpret that as 64-bit for most machines.
FYI, 32-bit FLOPs are useful in many situations, and machines had been on the top500 list that had used 32-bit FLOPs. You might take a look at our KASY0 FAQ on GFLOPS [aggregate.org]. As a means to rank the top500, I think it is quite legitimate to require 64-bit FLOPS, but that doesn't make it "illegal" to use 32-bit Linpack FLOPS for other comparisons.

As for the G5, it won't need AltiVec to get good Linpack numbers due to its fused multiply-add capability in its dual floating point pipes. That's 4 FLOPs per clock peak! I hope VT was able to get Apple to leave out, and not charge for, the components not needed in a cluster node. The PCI-X slots in the G5 should allow VT to better use a high-speed cluster network technology. Commodity x86 boxes tend to only have 32-bit 33MHz PCI, limiting the usable link bandwidth between nodes to under a gigabit per second. For 64-bit Linpack GFLOPS per dollar, a cluster of G5's could be competative. I look forward to seeing their results, and any similar work using the upcoming Athlon 64.

They use HyperTransport which was invented by AMD and used in Opertons.

So what? Did he say it was exclusive to PowerMacs? And Apple is a member of the HyperTransport consortium.

* On board gigabit ethernet.Huh? Such things exist in the x86 world as well.

But they usually aren't standard on the motherboard.

AltiVec cannot be used; it can only perform 32 bit floating point calculations which is not legal for the Linpack benchmark used at the top500 site.

Wonderful. Once you've gotten your "top 500" rating you can turn it back on and start spanking other clusters. Next?

The Apple G5 has far more fans than your typical x86 box

Which was done to reduce the amount of noise, not because the 970 puts out enormous amounts of heat.

Oh yeah -- they can't strike out the cost of buying a copy of MacOS for each machine, can they?

Hmm, lets think about this for a second. They're buying over a thousand brand new machines and giving Apple some great PR. Do you really think that Apple wouldn't come down on the price of the included operating system?